November 26, 2018

TPO Roofing: Thermoplastic Polyolefin Roof Systems

Thermoplastic polyolefin (TPO) is a top contender in plastic roofing, for several reasons. Read on to dive into the many layers of TPO roofing.

Time to read:
5 Minutes
Written by
Nicholas Capobianco

Roofing isn’t something that can be treated as an afterthought. It’s one of the most important parts of any residential or commercial structure, and protects the integrity of everything underneath it. Unfortunately, choosing the right roofing system can be confusing, costly, and a general pain in the neck for those unfamiliar with the different products available.

If you’ve purchased a new building that needs a roofing system upgrade or you’re replacing the roof on an existing property, you may have come across the term “TPO.” This layered roofing system is popular with buyers who want a solid product that won’t need to be replaced in the near future, and for good reason. Here’s why TPO roofing could be a contender for your building.

TPO roofing: the basics

TPO stands for thermoplastic polyolefin, which is the full name of the material used to make the roof membrane. When heat is applied, TPO becomes pliable and can be molded and fused into a watertight barrier. As it cools, the material hardens, becoming a durable layer that protects the roof from mother nature and internal heat loss, according to Energy Star.

A TPO roofing system uses several layers to attach the thermoplastic membrane to the roof, usually leaving the reflective white TPO layer exposed. It’s cost-effective, tough enough to withstand weather conditions from Toronto to Miami, and works beautifully for commercial buildings.

A TPO roofing system has many layers to it—if you are considering it as a solution to your roofing need, read on to familiarize yourself with their names and the role they each play in keeping buildings covered and secure.

Exploring the roofing layers

Installation of a TPO roof involves seven basic layers that all serve an important function.

1. TPO membrane

This is always the outermost layer of the TPO roofing system. The heating and cooling process specified above is used to seal the seams, and create that protective barrier. TPO is sold in thicknesses of 44, 60, and 90 millimeters. The thicker the membrane, the longer it will last before requiring replacement or maintenance.

2. Bonding adhesive

There are two ways to attach the TPO membrane:

  • Mechanical attachment: This is a cheaper method that uses fasteners to attach the membrane to the roofing deck along the seams. The membrane can be attached in lower temperatures, but the space between fasteners can shorten the life of the roof.

Since it’s not attached completely, strong winds can cause parts of the membrane system to blow and separate. Air from inside the building may fill these spaces, creating pockets of damp that eventually lead to the growth of mildew in the insulation. Mechanical attachment also reduces energy efficiency and can require the decking to be rated for a heavier load to compensate for wind gusts. 

  • Full adhesion: This involves an all-over adhesive that’s placed on the membrane and the layer to which it’s being attached.Full adhesion is exactly what it sounds like. This method costs more, but it eliminates the problems that come when the membrane separates from its base.

It also increases energy efficiency, prevents sound pollution, and provides an air barrier. The only drawback to full adhesion is the adhesive’s sensitivity to temperatures under 40° F, which makes it difficult to install during the winter.

3. Quarter-inch cover board

A cover board is usually made out of gypsum and works better to reinforce the membrane than insulation alone. This layer gives the TPO membrane something solid to attach to, and improves the long-term integrity and strength of the roof. The cover board isn’t always necessary, but is highly recommended when the roof is going to be exposed to additional stress.

4. Insulation

The standard insulation is made out of polyisocyanurate board, and comes in varying thicknesses. Like the TPO membrane, the insulation board can be attached in a few different ways:

  • Mechanically attached: This involves using five fasteners per 4x8 board to secure the insulation in place.Fully adhered:
  • Full adhesion requires another layer of substrate underneath the insulation boards. This means that the TPO membrane will be adhered directly to the insulation layer, and the insulation will need to be secured using between eight and 32 fasteners per board. This is what holds everything together and provides a strong outer layer.
  • Mechanically attached and adhered: Newly-poured concrete may not yet be a sturdy foundation for the rest of the roof. When this happens, both attachment and adhesion together is often appropriate.

5. Vapor barrier

A vapor barrier is a layer that’s meant to provide protection from inside air attempting to escape through the roof. This layer is appropriate in areas with colder climates and can stop you from having to purchase a new roof sooner than you would like.

6. Underlayment

Like the cover board, an underlayment is usually made out of gypsum and acts as an extra layer under the insulation. This can improve the fire rating for buildings that require it, but isn’t necessarily essential to the TPO roofing system.

7. Metal roof deck

The metal roof deck is the corrugated metal that sits underneath the other layers. Think of it as your commercial roof in the nude. The roof deck provides the initial foundation for a TPO roofing system.

The pros of a TPO roofing system

One of the biggest advantages to a TPO roofing system is the cost. It comes at a lower price point than almost any other option, while still providing a sturdy and dependable roofing system for commercial buildings.This roofing material can be fully adhered, mechanically fastened, or ballasted. TPO seam strengths are reported to be three to four times higher than EPDM roofing systems. This is a popular choice for “green” buildings for several great reasons: no added plasticizers, sunlight reflection, and resistance to UV radiation.

The white color works to reflect sunlight, improving energy efficiency. That’s because using white roof material helps reduce heat island effect and solar heat gain in the building. On top of this, it doesn’t require pressure washing or constant maintenance.

People who purchase TPO roofing systems also have options regarding the installation methods used and other factors which affect the overall cost of the project. Installers mechanically fasten poly-iso insulation to the roof deck, and stretch the TPO over the roof in big sheets, with seams heat-welded together. This is used a lot of industrial buildings, condos, and private homes. Typical lifespans range around 20 years, but can last up to 30 years!

You really can’t get a better result for the price.

The cons of a TPO roofing system

The biggest con for TPO roofing system is a lack of consistency between manufacturers. It’s important to trust your project with a company that takes pride in their work and only uses the highest quality materials. Ask your roofing professionals here at Roofr who they might suggest as a great manufacturer! Professional opinions are always best.

Another point of concern is the number of seams that can occur on a larger roofing project. If not properly treated, these seams can turn into weak spots. This problem can be minimized with proper heat welding and application, T-joints, and installation by one of our certified and vetted roofing contractors.

Consider the climate

As we pointed out, TPO roofing membrane is heat sensitive and needs to be installed in certain conditions to be effective. The key is to choose a season that allows for the most wiggle room in scheduling. Areas like Toronto may be best off installing TPO roofing outside of the deep winter. but this doesn’t mean that the system is out of the question in cooler climes.

Is TPO your answer?

The only way to really know whether a TPO roofing system is right for your project is to set up a consultation with experienced professionals in the roofing industry. Want to get a quote for TPO roofing? Reach out through our website. Have more questions? Ask us on Twitter @roofrapp.

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